5. Swarm

5.1. Enable Swarm

To start Swarm, type in the following.

1docker swarm init

You should see a similar output as follows.

Swarm initialized: current node (891q5gj0y69y2s1kzk01xdjzy) is now a manager.

To add a worker to this swarm, run the following command:

    docker swarm join --token SWMTKN-1-3mwknlzd6h75b0l8e9324l3tlhi1hhn1k9cc0vklwsf937v1dq-3ri0hmvm2390rho4irbwby0ru 192.168.0.73:2377

To add a manager to this swarm, run 'docker swarm join-token manager' and follow the instructions.

To list the nodes in the swarm.

1docker node ls

Output.

ID                            HOSTNAME            STATUS              AVAILABILITY        MANAGER STATUS      ENGINE VERSION
16ui13y7ijoaqw6u8h05u2a2b *   ryzen               Ready               Active              Leader              19.03.3

5.2. Set up a Docker registry

To set up a local Docker registry, type in the following.

docker service create --name registry --publish published=5000,target=5000 registry:2

mq4lk2beo4yz1hj8aqe2po3up
overall progress: 1 out of 1 tasks
1/1: running   [==================================================>]
verify: Service converged

Check the status as follows.

1docker service ls

ID                  NAME                MODE                REPLICAS            IMAGE               PORTS
mq4lk2beo4yz        registry            replicated          1/1                 registry:2          *:5000->5000/tcp

Check that it’s working.

1curl http://localhost:5000/v2/

5.3. Publish stack

Create docker-compose.yml as follows.

version: "3.7"
services:
  db:
    image: 127.0.0.1:5000/db
    build: ./mysql
    ports:
      - "3306:3306"
    volumes:
      - type: bind
        source: ./mysql/docker-entrypoint-initdb.d
        target: /docker-entrypoint-initdb.d
        consistency: consistent
    environment:
      MYSQL_ROOT_PASSWORD: "oneoffcoder"
  flask:
    image: 127.0.0.1:5000/rest
    build: ./flask
    ports:
      - "5001:5000"
    depends_on:
      - db
  ng:
    image: 127.0.0.1:5000/ui
    container_name: ui
    build: ./ng
    ports:
      - "80:80"
    depends_on:
      - flask
      - db

Build.

1docker-compose up

Publish.

1docker-compose push

5.4. Deploy to Swarm

Now deploy the stack to the swarm.

docker stack deploy -c docker-compose.yml student

Output.

Creating network student_default
Creating service student_flask
Creating service student_ng
Creating service student_db

5.4.1. List services

1docker service ls

Output.

ID                  NAME                MODE                REPLICAS            IMAGE                        PORTS
mq4lk2beo4yz        registry            replicated          1/1                 registry:2                   *:5000->5000/tcp
v898krzykppw        student_db          replicated          1/1                 127.0.0.1:5000/db:latest     *:3306->3306/tcp
bgkeb2k2skpt        student_flask       replicated          1/1                 127.0.0.1:5000/rest:latest   *:5001->5000/tcp
ypnuugzylzp7        student_ng          replicated          1/1                 127.0.0.1:5000/ui:latest     *:80->80/tcp

5.4.2. Inspect services

docker service inspect --pretty student_db
docker service inspect --pretty student_flask
docker service inspect --pretty student_ng

5.4.3. Scale services

docker service scale student_ng=5
docker service ps student_ng

5.5. Stop services

docker stack rm student
docker service rm registry

Output.

Removing service student_db
Removing service student_flask
Removing service student_ng
Removing network student_default

5.6. Leave swarm

To leave swarm.

docker swarm leave --force